Process for preparing organotin compounds

ABSTRACT

Provided is an efficient and effective process for preparing certain organotin compounds having alkyl and alkylamino substituents. The process provides the organotin compounds in a highly pure crystalline form which are particularly useful as precursors in the deposition of high-purity tin oxide films in, for example, extreme ultraviolet light (EUV) lithography techniques used in the manufacture of certain microelectronic devices.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 USC 119 of U.S. ProvisionalPatent Application No. 63/047,984 filed Jul. 3, 2020, the disclosure ofwhich is hereby incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

This invention belongs to the field of organotin chemistry. Inparticular, it relates to an efficient and effective process forpreparing certain organotin compounds, for example, isopropyltris(dimethylamido) tin.

BACKGROUND OF THE INVENTION

Certain organotin compounds have been shown to be useful in thedeposition of highly pure tin (II) oxide in applications such as extremeultraviolet (EUV) lithography techniques used in the manufacture ofcertain microelectronic devices. Of particular interest are organotincompounds having a combination of alkylamino groups and alkyl groups,which can be difficult to provide in high purity.

Accordingly, there is a need to provide an improved methodology formanufacturing such organotin compounds in highly pure forms for use inthe deposition of highly pure tin oxide films.

SUMMARY OF THE INVENTION

Provided herein is a process for preparing certain organotin compoundshaving alkyl and alkylamino substituents, such as a compound of Formula(I): R₁—Sn—(NR₂)₃ wherein R, which can be the same or different, is aC₁-C₄ alkyl group and R₁ is a substituted or unsubstituted saturated orunsaturated linear, branched, or cyclic C₁-C₅ group. A specific exampleof a compound having Formula (I) is isopropyl tris(dimethylamido) tin(CAS No. 1913978-89-8). The process comprises contacting a compound ofFormula (A), described in more detail herein, with a compound of FormulaR₁—X, wherein X is bromo, iodo, or chloro. The process also produces acompound of Formula (II), and the present invention also relates to thiscompound. Advantageously, the process provides the organotin precursorcompounds of Formula (I) in a highly pure form such as in greater than98% purity. Due to their high purity, the organotin compounds describedherein are particularly useful in the deposition of high-purity tinoxide (SnOx) films in, for example, extreme ultraviolet light (EUV)lithography techniques used in microelectronic device manufacturing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a crystal structure depiction of the compound of Formula (II)as a by-product of the process as set forth herein, wherein each R ismethyl and each X is iodo.

FIG. 2A and FIG. 2B are ¹¹⁹Sn-NMR and ¹-H-NMR spectra respectively takenin d6-benzene of the compound of Formula (I) as a product of the processset forth herein, wherein each R is a methyl group and R₁ is anisopropyl group.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a process for preparing organotincompounds having alkyl and alkylamino substituents.

In a first embodiment, the invention provides a process for preparing amonoalkyl tris(dialkylamido) tin compound of the Formula (I):

In this formula, each R may be the same or different and is a C₁-C₄alkyl group and R₁ is a substituted or unsubstituted saturated orunsaturated linear, branched, or cyclic C₁-C₅ group. The processcomprises contacting a compound of Formula (A)

with a compound having the Formula R₁—X, wherein X is bromo, iodo, orchloro. In an embodiment of this process, each R can be independentlychosen from a methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl,t-butyl, and sec-butyl group. In a particular embodiment, each R is amethyl group. Furthermore, R₁ can be chosen from a methyl, ethyl,propyl, isopropyl, n-butyl, isobutyl, t-butyl, sec-butyl, n-pentyl,iso-pentyl, or neopentyl group. In addition, R₁ can be a cyclic C₁-C₅group such as a cyclopropyl group. Also, R₁ may be an unsaturated C₁-C₅group such as a vinyl group or an acetylenyl group. Any of these R₁groups may be further substituted, such as with one or more halogengroups or ether groups. For example, R₁ may be a fluorinated alkyl grouphaving the formula —(CH₂)_(n)(CH_(a)F_(b))_(m), wherein m=1 to 5 andm+n=1 to 5 and wherein b=1 to 3 and a+b=3, including a monofluorinatedC₁-C₅ alkyl group, such as a —CH₂F or —CH₂CH₂F group, and aperfluorinated C₁-C₅ group, such as a —CF₃ or CF₂CF₃ group.Alternatively, R₁ may be an alkylether group, wherein the alkyl portionis a C₁-C₅ alkyl group. In a particular embodiment, R₁ is anunsubstituted C₁-C₅ alkyl group, such as a C₁-C₃ alkyl group. Forexample, each R may be methyl and R₁ may be isopropyl.

As shown above, the starting material used in this process is a compoundof Formula (A):

This compound can be prepared by known methods, such as, for example, byreacting tin(II) chloride (SnCl₂) with a compound of the formulaM-N(R)₂, wherein M is a metal chosen from sodium, lithium, andpotassium. Thus, an embodiment of the present invention is a process forpreparing a compound of Formula (I), which further comprises the priorstep of preparing the starting material of Formula (A) by reactingtin(II) chloride with a compound of Formula M-N(R)₂, wherein M is ametal cation, such as an Al, Mg, or Ca cation or a Group 1 or Group 2cation such as sodium, lithium, or potassium. As a specific example, Mcan be lithium and R can be methyl. In such a case, the lithium chloridethus formed may be removed, such as via filtration if desired, prior tocontacting the resulting compound of Formula (A) with the compound ofFormula R₁—X. Otherwise, the formed starting material compound ofFormula (A) can be used as is without filtration in the form of a slurrywith a compound of formula M-Cl (such as lithium chloride) havingprecipitated) for reaction in the same reaction vessel. Accordingly, theprocess of the present invention provides a one-pot synthesis of thecompound of Formula (I).

The reaction provides a mixture of the compound of Formula (I), as shownabove, along with a by-product of Formula (II):

wherein each R may be the same or different and is a C₁-C₄ alkyl groupand each X is chosen from iodo, bromo, and chloro. Accordingly, thepresent invention further provides by-product compounds of Formula (II).For example, in one embodiment of this by-product, each R is the same ordifferent and is a C₁-C₄ alkyl group and each X is chosen from iodo,bromo, and chloro, provided that when X is chloro, R is other thanmethyl. In another embodiment, each R is the same or different and is aC₁-C₄ alkyl group and each X is either iodo or bromo. The crystalstructure of a compound of Formula (II), wherein each R is methyl andeach X is iodo, is depicted in FIG. 1. These by-products of Formula (II)are also expected to be useful as precursor compounds for the depositionof tin oxide films (such as tin(II) or tin(IV) oxide films) as well asbeing useful as intermediates in the synthesis of other useful organotinprecursor compounds.

The process of the present invention can be conducted either neat (i.e.,without any added solvent) or in a solvent which is otherwisenon-reactive with the starting materials or products. Examples ofsuitable solvents are non-polar aprotic solvents including liquidhydrocarbons such as hexanes, benzene, or toluene; polar aproticsolvents such as tetrahydrofuran or dimethoxyethane; and mixtures ofnon-polar aprotic and polar aprotic solvents. When conducted neatwithout any added solvent, an excess of the compound of Formula R₁—X maybe used, particularly when this compound is a liquid. Also, the processmay be conducted via an exchange reaction, using a halogen exchangereagent in combination with the compound of Formula R₁—X.

The process is conducted at a temperature suitable for the disclosedreagents to react. For example, the reaction temperature may be in arange of from near room temperature (such as about 20° C.) to about 80°C. In a preferred embodiment, the process is conducted at a temperatureof room temperature (23° C.) to about 65° C., such as about 50° C. toabout 70° C. or about 60° C.

As noted above, in the synthesis of the starting material of Formula(A), the lithium halide by-product (e.g., LiCl) can be removed viafiltration. The resulting starting material can be used as-is in thesame reaction vessel for further reaction with the compound of FormulaR₁—X to form the compound of Formula (I), which can be further purified,such as via distillation, to provide a product having advantageously lowlevels of impurities.

The present invention can be further illustrated by the embodimentsincluded herein, although it will be understood that these embodimentsare included merely for purposes of illustration and are not intended tolimit the scope of the invention unless otherwise specificallyindicated.

EXAMPLE 1

Isopropyl tris(dimethylamido) tin was prepared using the reactionsequence as described above and shown below:

Thus, a 3-neck 500 mL round bottom flask equipped with a magnetic stirbar was charged with 12.2 g lithium dimethylamide (239 mmol) and 250 mLhexanes. To this off-white slurry was added 21.6 g SnCl₂ (113 mmol) andthe resulting mixture was stirred at 60° C. for 72 hours. The resultinggray-green slurry was cooled to 23° C., giving a mixture including thecompound of Formula (A).

Without further purification, the mixture was treated with 11.5 g2-iodopropane (68.2 mmol). The reaction mixture was then heated to 60°C. for 18 hours. After the reaction mixture had cooled to 23° C., it wasfiltered through a coarse porosity fritted filter into a 500 mL flask,and the filter cake was washed with a 500 ml aliquot of anhydroushexanes to give a light yellow clear solution. The solvent and othervolatiles were then removed from the filtrates under reduced pressure,to produce a mixture of product of Formula (I) and byproduct of Formula(II).

When the removal of volatiles was complete, the oil that remained wasfiltered through a 0.2 micron syringe filter to give 10.6 g of an orangeoil. The orange oil was placed in a −30° C. freezer overnight whichresulted in the precipitation of [ISn(NMe₂)]₂ as a yellow solid. Thisyellow solid was removed by filtration through a 0.2 micron syringefilter. The remaining orange oil was then distilled using a short-pathdistillation at 610-645 mtorr with a head temperature of 34-37° C. togive a isopropyl tris(dimethylamido) tin as a clear light yellow-greenoil distillate (6.09 g, 36.5%). ¹H-NMR (400 MHz, benzene-d6): δ 2.83(¹H-^(119/117)Sn)=n)=20.8 Hz, 18H), 1.68-1.57 (m, 1H), 1.27 (d,Eh-13C=7.3 Hz, 6H). ¹¹⁹Sn NMR: 64.30. The ¹¹⁹Sn-NMR and ¹H-NMR spectrumare shown in FIGS. 2A and 2B respectively, demonstrating that theproduct was of high purity.

The by-product, [ISn(NMe₂)]₂ was found to be a crystalline solid andtherefore also of high purity, such as greater than 95% pure, includinggreater than 98%, 99%, or 99.5%. The crystal structure is shown in FIG.1, and the crystallinity data is provided in Table 1 and Table 2. Due totheir high purity, these organotin compounds would be expected to beuseful in the deposition of high-purity tin oxide films in, for example,extreme ultraviolet light (EUV) lithography techniques used inmicroelectronic device manufacturing.

TABLE 1 Crystal data and structure refinement for [ISn(NMe₂)]₂.Empirical formula C4 H12 I2 N2 Sn2 Molecular formula C4 H12 I2 N2 Sn2Formula weight   579.34 Temperature   100.15 K Wavelength     0.71073 ÅCrystal system Orthorhombic Space group Pbcn Unit cell dimensions a =22.0958(5) Å α = 90°. b = 10.2623(3) Å β = 90°. c = 10.9856(3) Å γ =90°. Volume  2491.03(11) Å³ Z     8 Density (calculated)     3.090 Mg/m³Absorption coefficient     8.919 mm⁻¹ F(000)  2048 Crystal size 0.2 ×0.18 × 0.18 mm³ Crystal color, habit light yellow block Theta range fordata collection 1.843 to 27.102°. Index ranges −28 <= h <= 28, −13 <= k<= 12, −14 <= l <= 14 Reflections collected 25802 Independentreflections  2748 [R(int) = 0.0740] Completeness to theta = 25.242°100.0 % Absorption correction Semi-empirical from equivalents Max. andmin. transmission 0.2616 and 0.1599 Refinement method Full-matrixleast-squares on F² Data/restraints/parameters  2748/0/96Goodness-of-fit on F²     1.259 Final R indices [I > 2sigma(I)] R1 =0.0291, wR2 = 0.0713 R indices (all data) R1 = 0.0300, wR2 = 0.0720Extinction coefficient     0.00069(5) Largest diff peak and hole 1.367and −0.890 e.Å⁻³

TABLE 2 Bond lengths [Å] and angles [°] for [ISn(NMe₂)]₂ Lengths:I(1)—Sn(1) 2.8492(5) I(2)—Sn(2) 2.8448(5) Sn(1)—N(1) 2.252(4) Sn(1)—N(2)2.267(4) Sn(2)—N(1) 2.245(4) Sn(2)—N(2) 2.243(4) N(1)—C(1) 1.477(6)N(1)—C(2) 1.484(6) N(2)—C(3) 1.480(7) N(2)—C(4) 1.482(6) C(1)—H(1A)0.9800 C(1)—H(1B) 0.9800 C(1)—H(1C) 0.9800 C(2)—H(2A) 0.9800 C(2)—H(2B)0.9800 C(2)—H(2C) 0.9800 C(3)—H(3A) 0.9800 C(3)—H(3B) 0.9800 C(3)—H(3C)0.9800 C(4)—H(4A) 0.9800 C(4)—H(4B) 0.9800 C(4)—H(4C) 0.9800 Angles:N(1)—Sn(1)—I(1) 98.21(10) N(1)—Sn(1)—N(2) 78.97(14) N(2)—Sn(1)—I(1)95.40(11) N(1)—Sn(2)—I(2) 93.25(10) N(2)—Sn(2)—I(2) 92.67(11)N(2)—Sn(2)—N(1) 79.62(14) Sn(2)—N(1)—Sn(1) 97.25(14) C(1)—N(1)—Sn(1)118.1(3) C(1)—N(1)—Sn(2) 108.3(3) C(1)—N(1)—C(2) 108.3(4)C(2)—N(1)—Sn(1) 110.2(3) C(2)—N(1)—Sn(2) 114.5(3) Sn(2)—N(2)—Sn(1)96.88(15) C(3)—N(2)—Sn(1) 119.8(3) C(3)—N(2)—Sn(2) 105.7(3)C(3)—N(2)—C(4) 108.0(4) C(4)—N(2)—Sn(1) 110.1(3) C(4)—N(2)—Sn(2)116.5(3) N(1)—C(1)—H(1A) 109.5 N(1)—C(1)—H(1B) 109.5 N(1)—C(1)—H(1C)109.5 H(1A)—C(1)—H(1B) 109.5 H(1A)—C(1)—H(1C) 109.5 H(1B)—C(1)—H(1C)109.5 N(1)—C(2)—H(2A) 109.5 N(1)—C(2)—H(2B) 109.5 N(1)—C(2)—H(2C) 109.5H(2A)—C(2)—H(2B) 109.5 H(2A)—C(2)—H(2C) 109.5 H(2B)—C(2)—H(2C) 109.5N(2)—C(3)—H(3A) 109.5 N(2)—C(3)—H(3B) 109.5 N(2)—C(3)—H(3C) 109.5H(3A)—C(3)—H(3B) 109.5 H(3A)—C(3)—H(3C) 109.5 H(3B)—C(3)—H(3C) 109.5N(2)—C(4)—H(4A) 109.5 N(2)—C(4)—H(4B) 109.5 N(2)—C(4)—H(4C) 109.5H(4A)—C(4)—H(4B) 109.5 H(4A)—C(4)—H(4C) 109.5 H(4B)—C(4)—H(4C) 109.5

EXAMPLE 2

F₃CSn(NMe₂)₃ was prepared using the reaction sequence as described forExample 1. Specifically, [Sn(NMe₂)₂]₂ (23.1 g, 55.6 mmol) was loadedinto a 250 mL roundbottom flask equipped with a magnetic stir bar anddissolved in hexanes (125 mL). The flask was equipped with a cylinder ofI-CF₃ (25 g, 127.6 mmol) via a 1/4 PTFE tube and 24/40 tubing adapter.Slowly, the I-CF₃ was bubbled into the hexanes solution with stirring inthe dark. After approximately 10 minutes, the reaction presented with ayellow precipitate. After approximately 30 minutes, all of the gas hadbeen added, and the reaction presented with a flocculent yellowprecipitate. The cylinder was then removed and massed, confirming thatall of the desired I-CF₃ had been added. The reaction was covered withfoil and stirred at room temperature in the dark over the weekend. Afterthis time, the reaction presented as a yellow/tan precipitate and wasfiltered over a disposable polyethylene filter frit and washed withhexanes (25 mL). The resulting pale yellow solution dried under reducedpressure until approximately 5 mL remained. A ¹H-NMR, ¹⁹F-NMR, and¹¹⁹Sn-NMR of a C₆D₆ solution of the product showed hexanes stillremained (approximately 5 mol). A tan solid (28.7 g) was isolated alongwith 4 g (22.5%) of a slightly yellow liquid. ¹H-NMR (C₆D₆, 400 MHz); s,18H, 2.69 ppm; ¹¹⁹Sn-NMR (C₆D₆, 150 MHz); q, −153.07 ppm; ¹⁹F-NMR (C₆D₆,376 MHz); −42.7 ppm.

EXAMPLE 3

F₃CCH₂Sn(NMe₂)₃ was prepared using a procedure similar to that shown inExample 2. Specifically, [Sn(NMe₂)₂]2 (140 g, 336 mmol) was placed in a1 L schlenk flask equipped with a magnetic stir bar and diluted withapproximately 400 mL of hexanes to form a yellow mixture. I—CH₂—CF₃ wasplaced in a 250 mL additional funnel and attached to the schlenk flask.A slow addition rate was achieved (approximately 0.5-1 drop/sec), andthe 1 L flask was covered with aluminum foil and stirred in the dark.After approximately 2.5 hrs, addition of the I—CH₂CF₃ was complete, andthe resulting yellow mixture was stirred in the dark overnight at RT.After this time, the reaction presented with a bright yellow solidprecipitate and red/orange solution. The precipitate was isolated byfiltration through a disposable polyethylene filter frit into a 500 mLschlenk flask equipped with a magnetic stir bar. The filter cake waswashed with hexanes (approximately 30 mL), and the resulting orangesolution dried under reduced pressure to yield a light-yellow solutionwith a yellow precipitate. The mixture was filtered through a 0.2 umsyringe filter into two tared amber 40 mL vials to yield 87.91 g (78.5%crude yield) of the product as a pale-yellow liquid. ¹H-NMR, ¹⁹F-NMR,and ¹¹⁹Sn-NMR results of a 1:1 product: C₆D₆ solution: ¹H-NMR (C₆D₆, 400MHz); s, 18H, 2.66 ppm; q, 2H, 1.52 ppm; ¹¹⁹Sn-NMR (C₆D₆, 150 MHz); q,−62.47 ppm; ¹⁹F-NMR (C₆D₆, 376 MHz); q, −51.93 ppm.

The invention has been described in detail with particular reference tocertain embodiments thereof, but it will be understood that variationsand modifications can be affected within the spirit and scope of theinvention.

What is claimed is:
 1. A process for preparing a monoalkyltris(dialkylamido) tin compound of Formula (I):

wherein each R is the same or different and is a C₁-C₄ alkyl group andR₁ is a substituted or unsubstituted saturated or unsaturated linear,branched, or cyclic C₁-C₅ group; wherein the process comprises:contacting a compound of Formula (A)

with a compound of Formula R₁—X, wherein X is bromo, iodo, or chloro. 2.The process of claim 1, wherein each R is independently a methyl, ethyl,propyl, isopropyl, n-butyl, isobutyl, t-butyl, or sec-butyl group. 3.The process of claim 1, wherein each R is a methyl group.
 4. The processof claim 1, wherein R₁ is a methyl, ethyl, propyl, isopropyl, n-butyl,isobutyl, t-butyl, sec-butyl, n-pentyl, iso-pentyl, or neopentyl group.5. The process of claim 1, wherein R₁ is a cyclic C₁-C₅ group.
 6. Theprocess of claim 1, wherein R₁ is a vinyl group or an acetylenyl group.7. The process of claim 1, wherein R₁ is substituted with one or morehalogen groups.
 8. The process of claim 1, wherein R₁ is an alkylethergroup.
 9. The process of claim 1, wherein each R is a methyl group andR₁ is an isopropyl group.
 10. The process of claim 1, wherein X is iodo.11. The process of claim 1, wherein the process is conducted in anon-polar aprotic solvent.
 12. The process of claim 1, wherein theprocess further comprises preparing the compound of Formula (A) byreacting tin(II) chloride with a compound of Formula M-N(R)₂, wherein Mis sodium, lithium, and potassium.
 13. The process of claim 12, whereinthe compound of Formula M-N(R)₂ is Li—N(CH₃)₂.
 14. The process of claim12, wherein the process is conducted in one reaction vessel.
 15. Acompound of the Formula (II):

wherein each R is the same or different and is a C₁-C₄ alkyl group and Xis iodo, bromo, and chloro, provided that wherein X is chloro, R isother than a methyl group.
 16. The compound of claim 15, wherein each Ris the same or different and is a C₁-C₄ alkyl and X is iodo and bromo.17. The compound of claim 15, wherein each R is a methyl group and X isiodo.
 18. The compound of claim 17 in crystalline form and having thestructure as set forth in FIG. 1.